Post on 03-Jun-2018
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The Mesicopter
A Meso-Scale Flight Vehicle
Stanford University
Prof. Ilan Kroo, Dept. of Aero/Astro
Prof. Fritz Prinz, Dept. of Mech. Eng.
Graduate Students:
Peter Kunz, Gary Fay, Shelly Cheng, Tibor Fabian,Chad Partridge
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The Concept: Meso-scale Flight
What is a meso-scale vehicle?
Larger than microscopic, smaller than conventional devices
Mesicopter is a cm-scale rotorcraft
Exploits favorable scaling
Unique applications with many low cost devices
Objectives
Is such a vehicle possible?
Develop design, fabrication methods
Improve understanding of flight at this scale
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The Concept: Applications
Atmospheric Studies
Windshear, turbulencemonitors
Biological/chemical hazard
detection
Planetary Atmospherics
Swarms of low-mass mobile
robots for unique data on
Mars
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Why rotorcraft for meso-scale flight?
As Reynolds number and lift/drag decrease, direct lift
becomes more efficient
Compact form factor, station-keeping options
Direct 4-axis control
Scaling laws (and nature) suggest cm-scale
flying devices possible.
The Concept: Rotorcraft
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The Concept: Challenges
Insect-ScaleAerodynamics
3D Micro-Manufacturing
Power / Control /Sensors
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Challenges: Aerodynamics
Insect-scale aerodynamics
Highly viscous flow
All-laminar
Low L/D
New design tools required
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Challenges: Micro-manufacturing
Efficient aero requires 3-D rotor design with 50m cambered blades
Micro-motor design, construction
Integrated power, electronics
(a)
Equipment at Rapid Prototyping Lab
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Approach
Advanced aerodynamic analysis and
design methods
Novel manufacturing approaches
Teaming with industry for power and
control concepts
Stepwise approach using functional
scale model tests
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Approach: (Super) Scale Model Development
Meso-scale prototypes:
3g and 15g devices
Focus on rotor aero, power
Stability and control testbeds 3 prototypes (60 100g)
Focus on stability and control
Near-term applications
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Approach: Aerodynamics
Navier-Stokes analysis of
rotor sections atunprecedented low
Reynolds number
Novel results of interest to
Mars airplane program
Nonlinear rotor analysis
and optimization code
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Aerodynamics: Airfoil Analysis
New results for very low Reairfoils
Very thin sections required
Maximum lift increases as Re
decreases below 10,000
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Aerodynamics: Airfoil Analysis
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Aerodynamics: Airfoil Analysis
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Aerodynamics: Section Optimization
Nonlinear optimization coupledwith Navier-Stokes simulation
New very low Re airfoil designs
Improved performance compared
with previous designs
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Aerodynamics: Section Flight Testing
Micro sailplanes permittesting of section properties
Difficulties with very lowforce measurements in wind
tunnel avoided
Optical tracking system
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Aerodynamics: Rotor Optimization
Chord, twist, RPM, blade number
designed using nonlinear optimization
3D analysis based on Navier-Stokes
section data
Rotor matched with measured motor
performance
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Approach: Rotor Manufacturing
1. Micro-machine bottom
surface of rotor on wax
2. Cast epoxy
3. Remove excess
epoxy 4. Machine topsurface of rotor
5. Melt wax
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Rotor Manufacturing: Materials and Methods
Wide range of rotor designs
fabricated and tested
Scales from .75 cm to 20 cm
Materials include epoxy,
polyurethanes, carbon
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Rotor Manufacturing: Validation
Scanning electron
microscopy to verify section
shape
3D laser scans to determine
as-built camber, twist
Machining process revised
based on initial results
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Aerodynamics: Rotor Testing
Milligram balance
Precision test stand
Torque and force
measurements
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Approach: Power and Control Systems
Energy storage
Motors
Sensors and Control
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Power and Control Systems: Energy Storage
Power sources tested
COTS batteries (NiCd, NMH, AgZn,
Lithium, in many sizes) Super-capacitors
SRI developing direct-write batteryunder DARPA program. High energy
density system integrated with small-
scale structure. Still under development.
Future technologies may include LiSO4,
micro fuel cells, micro-turbines.
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Power and Control Systems: Battery Scaling
Batte ry Pe rformanc e
1
10
10 0
1000
0.1 1 10 100
We ight (g)
SpecificEnergy
(mWH/g)
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Power and Control Systems: Motors
Small scale motors studied Smoovy 3mm, 5mm
MicroMo 1.9mm
Larger, efficient DC motors
Westech series, Smoovy 8mm
Inexpensive prototype Mabuchi motors
Micro-motor development
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Power and Control Systems:Sensors / Control Laws
Innovative passive
stabilization under test at
larger scale
Linear stability analysis
suggests configuration
features
MEMS-based gyros provide
damping
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Approach: Prototypes
Initial 3g device with external
power, controllers
Basic aero testing complete Issues: S&C, electronics
miniaturization, power
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Approach: Prototypes
Capacitor powered mesicopter
5mm Smoovy Integrated electronics
Shrouded frame
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Approach: Prototypes
Low cost unaugmented
60g system
Includes receiver, speed
controllers, lithium
batteries
Tethered flights to date
Sufficient lift for added
flight control electronics
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Approach: Prototypes
PC-board system with
digital communication
and on-boardmicrocontroller
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Approach: Prototypes
Larger 100g device
WesTech coreless motors
Significant payload capability
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Approach: Prototypes
Mars rotor design and test
Rotor designed for Mars atmosphere
Fabricated using mold, carbon epoxy
Test at JPL in Mars environment
chamber
Results encouraging, but incomplete
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Current Work
Continued rotor testing, optimization
Focus on stability and control issues
using testbeds
Integration of electronics
Closed-loop autonomous flight
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Future Work
Near-term applications
Mars rotorcraft
Testbed for multi-agent, cooperative control
Longer term aspects
Alternate power source potential Further miniaturization of electronics
New sensor concepts